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My monitors are not switching off (to power saving) when the screen is locked.

I have Ubuntu 20.04, a radeon graphic card and 3 Iiyama LED monitors (connected over HDMI/DP). When the systems get's locked (idle), the monitors are getting completely black (no backlight) but 5-10 seconds later they are getting back on, just a black screen (with backlight on) and the mouse cursor is visible. And it stays like that.

This behavior started after I connected these 3 LED monitors. Before I only had two if them and one LCD monitor. I also tried to reconnect the LCD monitor again but this behavior persists.

I already searched a lot but non of the results got my closer to a solution.

I tried it with this command, but it's still the same.

sleep 0.5
xset dpms force off
gnome-screensaver-command -l

I checked xset -q which looks good for my understanding:

Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  0    cycle:  0
DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On

At the moment the only way to save energy when not working on the machine is to switch the monitors off manually at the switch.

Hope someone has some hints to direct me to a solution.

Sebastian Koch
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    Hey, I have the same issue. Dual monitor setup. Would be also very interested in a solution. – chris.mccoy Apr 11 '21 at 15:50
  • @chris.mccoy Did either of you find a solution yet? It's happening for me too with my external Dell monitor (Ubuntu 20.04 on Lenovo E15, not using the built-in screen). – Ryan Jul 27 '21 at 16:14
  • https://askubuntu.com/questions/1240575/automatic-screen-lock-not-working-ubuntu-20-04 feels related. – Ryan Jul 27 '21 at 20:41
  • @Ryan Unfortunately I haven't. I am using a workaround currently. Either sending the whole system to sleep (that turns off the monitors completely) or turning them off manually with the power button. – chris.mccoy Jul 28 '21 at 17:30
  • @chris.mccoy Luckily mine suddenly started sleeping properly (automatically) today. So now I'm focusing on trying to fix these 2 major problems: https://askubuntu.com/questions/1324537/ubuntu-20-04-dual-boot-crashing-wondering-if-fix-is-available#comment2317340_1324537 and https://askubuntu.com/questions/1231441/ubuntu-screen-flickering/1231443#comment2315453_1231443 – Ryan Jul 28 '21 at 18:12

3 Answers3

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I found this answer on the Unix & Linux Stack that suggested it is the monitor's Input Source Auto-select feature. Disabling that on my three monitors solved my problems. If any were auto-select when the system blanked them they blanked for a few seconds then came on. I guess the auto-select function is seen by the system as activity.

Now I need to get someone to fix the head-shaped holes in my walls...

NotTheDr01ds
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Ted M
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1

For me the solution was to not connect any of the monitors over HDMI. Sounds strange but this helped.

I have 3 Iiyama G-Master (1x GB2760QSU with DP cable, 2x GB2730QSU one with DP cable and one with DVI cable) and a Radeon RX 580. Whenever I connect one of them with a HDMI cable I have this issue. I tried it with different combinations and different cables. As long as one Iiyama is connected with HDMI I've the same issue.

I also tried only two Iiyama monitors and one Samsung. With this installation it's possible to connect even the Iiyama over HDMI with no issue.

Sounds strange but this is my solution.

Sebastian Koch
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0

[I can't comment to the particular post because not enough rep on StackExchange, but wanted to share my experience...original post from above for context]

I found this answer on the Unix & Linux Stack that suggested it is the monitor's Input Source Auto-select feature. Disabling that on my three monitors solved my problems. If any were auto-select when the system blanked them they blanked for a few seconds then came on. I guess the auto-select function is seen by the system as activity.

This technique of just changing the input source of 1 of my 3 monitors (Ubuntu 22.04) to not be auto-select fixed this problem for me. I've had this problem since installing 22.04, so I am happy to provide a confirmatory datapoint that this approach is efficacious.

Steve Byrne
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